1. Field of the Invention
The present invention relates generally to apparatus and methods of closing and sealing chemical reactor vessels and specifically to closure systems, for such vessels, which are relatively less susceptible to contaminant build-up and more easily maintained in such a state.
2. Background of the Prior Art
Glass and enameled reactor vessels have become well known and broadly used for carrying out elevated or reduced temperature and/or elevated or reduced pressure chemical reactions as well as the blending (mixing) of non-reacted elements or compounds. Such vessels may be jacketed, having one or more additional partial or full shells surrounding, but spaced apart from, the vessel wall. The space between the shells or between the shell and the vessel wall may be filled with gas, liquid or solid materials either as a static medium, such as a low heat conducting solid material for insulation or in a dynamic state, i.e., flowing liquid and/or gas for cooling and/or heating purposes.
Where such vessels are used in certain applications such as, for examples, in the food industry and, in particular, in the pharmaceutical industry, cleanliness and the ability to continuously maintain cleanliness are of the utmost importance.
Typically, the inner surfaces of such vessels are coated with glass, vitrified enamel or some other generally non-metallic, corrosion, erosion and/or temperature-resistant material. Many of these materials, e.g. glass, tend to be relatively brittle and prone to fracture upon impact or significant distortion. Therefore, it becomes necessary, in order to successfully attach heads, covers, tops, fixtures, piping, etc. to such vessels, to use specialized joints which will diminish and, essentially, eliminate the risks of the glass cracking or otherwise failing. Such joints are typically designed to diminish localized flex-induced stress and to otherwise uniformly distribute stress and strain, both at ambient temperatures and at elevated temperatures. An example of an enameled, jacketed vessel, and the joints used to attach the head to the vessel, are shown in U.S. Pat. No. 2,330,306. Note that in several embodiments of U.S. Pat. No. 2,330,306, a removable sheet metal cover is telecoped down over the upwardly curved part of the head to form a joint cover. In this design, dirt and contamination can readily accumulate at the unsealed joint where the perforation in the sheet metal cover abuts the curvature of the head.
Typical designs of such joints frequently include two parallel glass or enamel coated surfaces, facing each other, with some form of a gasket and/or other deformable material therebetween. Also included are means, such as a combination of relatively heavy flanges and clamps, arranged to impose uniform force, without localized flex-induced stress, urging both coated surfaces towards each other. The structure supporting those surfaces must be sufficiently rigid to uniformly distribute such force, without distorting those surfaces, to effect uniform compression or deformation of the gasket or other interspaced materials, thus sealing the two glassed or enameled surfaces sufficiently to, for example, enable the joint to contain high internal pressures, at elevated temperature in some cases, within such vessels. Alternatively, the vessel application may be at ambient or even cryogenic temperatures and the pressure may be external, i.e., a vacuum is being imposed within the vessel. A typical example of such a heavy rigid flange clamping arrangement is seen in U.S. Pat. No. 2,967,699.
The pharmaceutical industry, as mentioned above is extremely sensitive to cleanliness in all aspects of its manufacturing processes, deeming it of great importance to eliminate contaminants and enhance purity values. Much of the impetus for such a policy is founded upon a myriad of governmental regulations which dictate standards of sanitation, cleanliness, sterilization and purity to a heightened degree which is not generally applicable to other segments of the chemical industry. To enhance the ability of the pharmaceutical industry to comply with such expectations and standards, it is not only necessary to insure cleanliness to those areas of equipment which directly contact the actual chemical reactions, etc., which are carried out in the production of pharmaceuticals, but it is also necessary to design all equipment elements, even those portions which are remote from the actual chemical reactions, to be and remain as contaminant-free and clean as possible. In one sense, this means eliminating and/or diminishing as much as reasonably possible, those aspects of any given apparatus which tend to collect contamination or "dirt". In another sense, this means designing the various elements of apparatus for ease and facility of cleaning. Specifically, this means that there is a need for an enhanced means for connecting covers, or heads, to reactor vessels which are relatively contaminant free and easier to clean in comparison to those systems which are conventionally used throughout the general chemical processing industry.
Chemical reactor vessels have generally used clamping systems to join abutting flanges, covers or heads to the body or shell of the vessel. Frequently, these clamping systems include separate and distinct clamping mechanisms sometimes movably attached to the covers or heads, sometimes movably attached to the body or shell of the vessel and sometimes entirely separable, i.e. removable, from the joints formed between the abutting flanges. Such clamping mechanisms contain exposed screw mechanisms, or over-riding cam mechanisms, all of which have multiple complex and relatively tiny crevices, corners and pockets in which contaminants can build up and which are somewhat difficult to clean, and continuously keep clean, without removing the clamping mechanism from the joint or, at least, relaxing the force imposed on the joint by the clamping mechanism. This causes problems and concerns. Firstly, the facility to readily accumulate contamination is not at all desirable. Secondly, the inability to frequently and periodically remove the contamination build up, without shutting down the chemical reactor, is unacceptable. The more susceptible to contamination build up and retention a clamping mechanism is, the more frequently it must be cleaned and the more difficult it is to keep clean. Also, the care that must be exercised in cleaning must be more intense.